This chapter aims to provide an analysis of the role eugenic expert discourses played in the construction of the Swiss welfare state, as well as their effects on Swiss national identity. It explores the influence of eugenics on Swiss social policies, and shows how eugenic ideas and policy practices formed the basis for mechanisms of exclusion, from the Swiss national order, of categories of citizens deemed "unfit". The science of eugenics emerged during the second half of the nineteenth century, with the aim of assisting nation-states to formulate social policies which would improve the "quality" of the population. The emergence of modern techniques of government, including the growth of health and social policies from the turn of the twentieth century, provided the institutional conditions for translating the eugenic rhetoric into a concrete policy programme. The Swiss case is interesting in that it pioneered a number of eugenic ideas and policies in Europe, some of which continued until well into the post-war period. Swiss eugenic policies were mostly articulated from within a social-democratic perspective. They were closely bound up with the emerging welfare system and shaped by the specific Swiss political institutions, in particular federalism.